Devices for measuring rotational speed are required for instance for the measurement of the wheel speeds for anti-lock control systems, traction slip control systems or vehicle suspension control systems of automotive vehicles. In such applications, every vehicle wheel is equipped with such a wheel sensor. High demands are placed on the operability and reliability of the sensors. A major portion of the total costs for such a control system is incurred for the manufacture and the assembly of the sensors. It is in particular required in known rotation measuring devices to accurately adjust and preserve the air gap between the stationary transducer or sensor, respectively, and a toothed disc coupled to the wheel. The usefulness of the signal and the distance of the useful signal from inevitable corrective signals is dictated to a large degree by the adjustment and the preservation of the air gap. Therefore, there is a need to develop sensors which allow manufacturing with relatively little effort and which lend themselves to ease of assembly and, if necessary, ease of replacement.
Further, so-called wheel bearing sensors are known wherein the sensor and the pulse generator ring (or the toothed disc) are mounted directly into the wheel bearing. As a result, the sensor is required to fit within small spaces. However, precise assembly and adjustment is still necessary because tolerances for the air gap between the sensor and the pulse generator ring have to be maintained.